This invention relates generally to endodontic therapy and, more particularly, to the restoration of a dead or severely decayed tooth by preparing and filling the tooth's root canal with the assistance of optical techniques such as induced fluorescence spectroscopy.
The restoration of a dead or severely decayed tooth requires the tooth's root canal to be cleaned and sealed. The structure of a typical tooth 10 is shown in FIG. 1. The tooth has a crown 12 which extends above the gums 14 and is covered by enamel 16. At the heart of the tooth is the relatively soft living pulp 18 which includes blood vessels 20 and nerves 22. A hard substance called dentin 24 surrounds the pulp. The tooth also has one or more roots 26 below the gums that fit into sockets in the jawbone 28. Each root is covered by a sensitive, bone like material called the cementum 30. Within each root is a root canal 32. The root canal's structure may have dramatic curvatures and other complex microstructures at almost any position within the root. At the end or apex 34 of the root canal is a small opening, also called the apical foramen, through which the tooth's blood vessels and nerves enter into the root canal.
The ultimate success of the restoration of a tooth 10 is directly dependent upon the preparation of each root canal 32 and the integrity of the seal of the apex 34. Each root canal must be thoroughly cleaned eliminating tissue remnants, bacteria and antigenic inflammatory chemicals. Inadequate cleaning of the root canal may lead to short-term treatment failure, as well as long-term problems such as persistent inflammation and/or infection. Inadequate sealing of the apex 34 may allow contaminates to enter the root canal which may lead to persistent problems with or even failure of the tooth's restoration. The reintroduction of irritants and the slow dissemination of pathogenic substances through an unsealed opening exit is the most common cause of long-term endodontic failures.
Also, in conventional endodontic therapy, the root canal 32 must be shaped to allow controlled total filling of the root canal in all dimensions. Since a root canal frequently has an irregular structure, the shaping of the root canal must be carefully performed. As shown in FIGS. 2A and 2B, typical endodontic instruments, such as files 36 and the like, are much harder than the tooth's dentin 24 and tend to go in straight paths when used incorrectly. Such misuse of an endodontic file tends to cause blockages, ledges, via folsas 37, and perforations 38, all of which tend to decrease the chances of a successful tooth restoration. Also, incorrect use of a file may lead to overinstrumentation wherein too much healthy dentin is removed from the tooth which also tends to decrease the chances of a successful restoration.
As the root canal 32 is cleaned and shaped, the opening at the apex 34 of each root canal must be precisely located and prepared for sealing. The location and preparation of the opening greatly determines the effectiveness of the apical seal.
The proper preparation of the root canal 32 and location of the apex 34 typically requires a preoperative radiograph to gain insight into the size, shape and location of the root canal. However, the apical third of the root canal is obscured by the jawbone and tends to disappears from view on an x-ray image. The lack of a clear x-ray image of the apical third of the root canal adds to the uncertainty of the root canal's structure and the ultimate success of the restoration since this region of the root canal is where usually most of the root canals structural complexities are found. Certainly, more potential for irreversible damage exists in the apical third of a root canal than in the coronal two-thirds of the canal system. Other methods for determining the length of the tooth such as radiographs, tactile sense, and electronic apex detectors are not always able to precisely detect the location of the opening at the root canal's apex.
From the discussion above, it should be apparent that there is a need for a root canal explorer that can remove infected dentin with a minimum loss of healthy dentin, that can locate the opening at the root canal's apex, and that can seal the apex and fill the root canal while being relatively simple and rapid to use, and that provides lasting results. The present invention addresses these needs.